Hertha Berlin winger Jean-Paul Boetius will be sidelined after a tumour was found in one of his testicles.
The Dutchman, 28 was diagnosed during a routine medical check-up on Wednesday and will undergo surgery on Friday.
He played once for the Netherlands in 2014 and joined Hertha last month.
"We are full of hope and confidence that Jean-Paul will get healthy and return to our group as soon as possible," said the club's sports director Fredi Bobic.
"Until his return he will get from us all possible support. We will be tight as Hertha family and wish him all the very best."
Hertha said Boetius will be out for the foreseeable future and that they will provide further information on his recovery in due course.
Boetius has spent the last four seasons with Mainz and the ex-Feyenoord player will be the second Bundesliga player in two months to have a testicular tumour removed.
Former West Ham striker Sebastien Haller had surgery in July after being diagnosed during Borussia Dortmund's pre-season training camp.